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Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity

Maaroufi, Nadia I. ; Nordin, Annika ; Palmqvist, Kristin ; Hasselquist, Niles J. ; Forsmark, Benjamin ; Rosenstock, Nicholas P. LU ; Wallander, Håkan LU and Gundale, Michael J. (2019) In Global Change Biology
Abstract

There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha−1 year−1) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha−1 year−1). Our... (More)

There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha−1 year−1) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha−1 year−1). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (≤12 kg N ha−1 year−1) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.

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author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
carbon sequestration, ecological stoichiometry, Gadgil effect, high-throughput sequencing, ingrowth mesh bags, ITS amplicons, litter decomposition, root exclosure, soil organic matter
in
Global Change Biology
publisher
Wiley-Blackwell
external identifiers
  • scopus:85068798269
ISSN
1354-1013
DOI
10.1111/gcb.14722
language
English
LU publication?
yes
id
5d9270ac-9ad9-40ba-8f74-9b4b65b78306
date added to LUP
2019-07-24 16:34:25
date last changed
2019-12-03 02:17:07
@article{5d9270ac-9ad9-40ba-8f74-9b4b65b78306,
  abstract     = {<p>There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha<sup>−1</sup> year<sup>−1</sup>) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha<sup>−1</sup> year<sup>−1</sup>). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (≤12 kg N ha<sup>−1</sup> year<sup>−1</sup>) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.</p>},
  author       = {Maaroufi, Nadia I. and Nordin, Annika and Palmqvist, Kristin and Hasselquist, Niles J. and Forsmark, Benjamin and Rosenstock, Nicholas P. and Wallander, Håkan and Gundale, Michael J.},
  issn         = {1354-1013},
  language     = {eng},
  month        = {06},
  publisher    = {Wiley-Blackwell},
  series       = {Global Change Biology},
  title        = {Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity},
  url          = {http://dx.doi.org/10.1111/gcb.14722},
  doi          = {10.1111/gcb.14722},
  year         = {2019},
}